1. Field of the Invention
The present invention relates to an Otto cycle internal combustion engine with five valves per cylinder. The present invention relates in particular to a combustion chamber configuration and the related distribution architecture associated thereto.
2. Description of the Related Art
An internal combustion engine with five valves per cylinder is described for example in U.S. Pat. No. 5,868,113 in the name of Yamaha. This document describes an engine having a lens-shaped combustion chamber able to obtain a high compression ratio and to reduce the possibility of knocking. The engine described in the Yamaha US Patent includes a head having three intake valve and two exhaust valves. The intake and exhaust valves are arranged with an acute angle relative to the axis of the cylinder. Consequently, the combustion chamber is obtained for a relevant portion in the head.
The sum of the experiences collected with this configuration shows that engines of the type described in the aforesaid US patent are provided with a high volumetric efficiency, whereto however corresponds a low thermodynamic efficiency.